1. The Field of the Invention
This application relates generally to a spearhead assembly that is used for in-ground drilling.
2. The Relevant Technology
In some processes of down-hole drilling, a wireline and hoist may be used to lower and retrieve various tools or other down-hole objects in and out of the borehole. For example, a wireline may be connected to an overshot assembly and then used to lower or retrieve a spearhead assembly that is connected to a core barrel assembly. When retrieving such assemblies, the wireline and hoist often elevate the core barrel assemblies until they are completely extracted from the borehole. At that point, the lower end of the core barrel assembly may be moved away from the borehole and then lowered so as to lay flat on the surface of the earth. As the coupled overshot, spearhead, and core barrel assemblies are lowered, very high loads can be placed on various parts and cause bending or breaking of those parts.
In order to reduce the danger and damage associated with moving the coupled assemblies, some drilling processes have begun using jointed spearheads that contain a spearhead portion that is pivotally connected to a base portion. Because of the pivotal connection, the stress from the loads may be reduced. But the spearhead portion may also pivot from side to side and become locked against an internal surface of the borehole (or a drill string in the borehole) where it cannot be coupled with an overshot assembly for retrieval.
To avoid such problems, the spearhead portion of some jointed spearheads may be biased to a position that is convenient for coupling with the overshot. For example, some jointed spearheads may comprise a spring that biases the spearhead portion to one or more positions in relation to the base portion. Nevertheless, the design of some jointed spearheads may impose various limitations, i.e., causing the spearhead to be weak near the pivot joint. Accordingly, when such joints are misused or overloaded, deformation, accidental uncoupling, or failure may occur.
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced.